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Old 06-04-2018, 09:47 AM   #1
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Shaft log mid bearing?

Hi All,

I posted last year when we got the good ship, I had 5 gallons a day dripping from the shaft log entrance into the boat. There was a crossmember with a fitting for the packing bolted to the crossmember. The guys at the yard ground out all remnants of the rotted crossmember, dug out the years of (attempted) repairs and this is what I have now. A fitting will screw onto the shaft log and my dripless will go onto the fitting. And that's it... straight to the transmission. I've read about these old boats having only one bearing way at the back. But boy, engine alignment now is going to be SUPER critical. Wearing into the shaft log IS NOT AN OPTION! Does anyone else have such a setup?

Dave
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Old 06-04-2018, 10:06 AM   #2
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No flex hose between shaft log and seal? You want some flex there and your rig looks rigid.

And stainless steel for a shaft log? SS can corrode rapidly in some applications, not my first choice of material.

Whether you need a mid point bearing depends on shaft length, dia and rpm.
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Old 06-04-2018, 11:36 AM   #3
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Stainless was a mistake. There is still a good reason to use bronze. Make sure the yard gives you a guarantee, a long one.
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Old 06-04-2018, 11:44 AM   #4
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The boat I just bought has two cutless bearings and hence a rigid driveline, so I'm interested in the answer as well. It seems like it makes the engine alignment supercritical, and given a rubber mounted engine nearly impossible to achieve over all the operating conditions. Maybe the solution is a driveline saver type of flexible coupling, or maybe one of these Sigmadrives?
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Old 06-04-2018, 12:01 PM   #5
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The shaft log is original equipment... 40 years old. The part you see in the photo was just cleaned up. I don’t think it’s stainless.
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Old 06-04-2018, 12:59 PM   #6
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Just talked to the yard. They are getting a new PSS and clamping it directly onto the shaft log. They said they just got done with an old Ocean Alexander twin that was just like this... no center support. I asked the manager to inspect his mechanic's alignment job BEFORE they push the PSS onto the shaft log. I guess the bright side here is that the boat is 40 years old and after inspection of everything, the shaft has never been riding on the log anywhere... so it does work.
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Old 06-11-2018, 11:27 PM   #7
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Different than ours Dave. We have the traditional bronze going to a rubber hose that holds the packing gland. Old but simple. BUT, as you know a lot of unsupported shaft with mine!
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Old 06-12-2018, 05:23 AM   #8
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What is the distance from the dripless to the transmission?

Ted
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Old 06-12-2018, 08:32 AM   #9
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Quote:
Originally Posted by O C Diver View Post
What is the distance from the dripless to the transmission?

Ted
Good 5'. The old traditional stuffing box, mounted to a cross member was in fact kind of a center support for the shaft which is about 9-10' long. Once the stuffing was removed from the box and a dripless was installed, the shaft basically became unsupported in the center. Been running like that for over 11 years. So if I get a good engine alignment... we'll be OK. The most important thing was getting the log shaft sealed up and stopping the water from coming into the boat.
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Old 06-12-2018, 09:02 AM   #10
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Quote:
Originally Posted by DDW View Post
The boat I just bought has two cutless bearings and hence a rigid driveline, so I'm interested in the answer as well. It seems like it makes the engine alignment supercritical, and given a rubber mounted engine nearly impossible to achieve over all the operating conditions. Maybe the solution is a driveline saver type of flexible coupling, or maybe one of these Sigmadrives?
It looks like SigmaDrive's solution is a CV joint, which is OK, but needs lubrication...

What about this?
https://www.thompsoncouplings.com/pr...son-couplings/
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Old 06-12-2018, 10:08 AM   #11
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I have a cutless bearing on n my shaft log. Seems to make sense to me.
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Old 06-12-2018, 10:13 AM   #12
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Which dripless are you using, Tides or PSS? The PSS has a compressible corrugated hose that will tolerate some flexing.

Ted
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Old 06-12-2018, 10:38 AM   #13
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Quote:
Originally Posted by stubones99 View Post
It looks like SigmaDrive's solution is a CV joint, which is OK, but needs lubrication...

What about this?
https://www.thompsoncouplings.com/pr...son-couplings/
In the size needed for this HP, the Thompson also looks like a CV joint - rather two of them. And don't seem to be rated for thrust. The unique thing about the Sigmadrive is that it is a CV joint rated for thrust.
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Old 06-12-2018, 12:47 PM   #14
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In the size needed for this HP, the Thompson also looks like a CV joint - rather two of them. And don't seem to be rated for thrust. The unique thing about the Sigmadrive is that it is a CV joint rated for thrust.
So the flange bearing isn't a thrust bearing?

Does the fixed shaft move underway?
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Old 06-13-2018, 09:15 AM   #15
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Quote:
Originally Posted by o c diver View Post
which dripless are you using, tides or pss? The pss has a compressible corrugated hose that will tolerate some flexing.

Ted
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Old 06-13-2018, 12:37 PM   #16
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I had a stern tube leak 12 years ago.

Through the starn tube imbedded totally in concrete ballast. All had to be removed. The metal in the ballast was corroding and expanding.

Fixed it w a new FG laminated on a dowel. They make them (where I got mine) in Bellingham where the old Uniflite/Chris Craft plant was. Near the Ak ferry terminal.

Attached my dripless seal in the usual way to the fwd end of the tube.

Been trouble free since.
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Old 08-07-2018, 05:02 PM   #17
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Dave, do you mind me asking how much this project cost you? The shaft log in my '78 CHB is leaking (just went from a drip to a trickle yesterday) and I've read posts that say the cost of fixing it is more than the boat is worth. I haven't diagnosed the problem entirely, but want to get a sense of what I might be in for. Would appreciation your input, thanks.
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Old 08-10-2018, 06:14 AM   #18
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There are (costly) center ball bearing units that are split and can be installed without removing the shaft.


Proper bearing spacing is in Skeens Elements , at your local library.
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